Each term in the right hand side of (REF ) is given by the interpolation error (see e.g. [1]}),
\(\vert \kappa (x,y) - \kappa ^{(r)}(x,y) \vert = \frac{| \omega (x) |}{r !} \,\vert \partial _x^r \kappa (\xi ,y) \vert , \qquad \xi \in [\min _{i \in {\tau }} x_i , \max _{i \in {\tau }} x_i],\) 
